Time course of memory relocation revealed

The time-dependent role of the hippocampus in memory storage
has been revealed through new research led by UCL and the Massachusetts Institute of Technology (MIT).

The paper, published
in PLOS ONE, investigated the dynamic nature of memory storage in the brain -
studying the role of the hippocampus in the storage of contextual memories in rodents.

The hippocampus,
a brain structure within the medial temporal lobe in humans, is necessary for
storing recent experiences into memory. However, the hippocampus only acts as a
temporary storage for memories, as older memories are eventually transferred to
other parts of the brain for long-term storage.

To observe this
process more precisely, researchers used a molecular-genetic tool (DREADDs: Designer
Receptor Exclusively Activated by Designer Drugs), to remotely and reversibly
inactivate the hippocampus at multiple time points after the initial formation
of a memory, and study the time-dependent involvement of the hippocampus in
memory storage.

The researchers,
led by Dr Daniel Bendor (UCL Experimental
Psychology) and Dr Carmen Varela (MIT), found
that after 4-7 weeks contextual fear memories in rodents no longer require the
hippocampus, an indication that the memory is transferred to extra-hippocampal
brain regions such as the neocortex. These results support earlier research
demonstrating that hippocampal lesions disrupt recent memories but not older,
more remote memories.

Understanding the
time course of the relocation of memories from initial storage regions to
permanent storage sites in the brain is an important step for developing new
therapies for memory related disorders such as Dementia.